Misc. Comments

Grove lists the instrumentation of this piece as being "wind insts, Turkish band". Though a nocturne is supposed to be a "night piece", and one would normally associate that with restfulness, this piece in its original form is as noisy as one would expect of a band employing Turkish band types of instruments. Various instruments, notably the clarinet, have soloistic roles to play, and the percussion doesn't play in all the movements.

A nocturne did not take on the "restful" meaning now associated until John Field's piano pieces of that name (around this time, true- don't know if Spohr knew them, but - different context, anyway). Notturnos by Mozart and others are like serenades and divertimenti of the time, meant for open-air performance, often in the background, at and for various occasions (Mozart wrote a number of very good works indeed of this kind...) - Schissel (edit: often night-time occasions, hence, night pieces, one guesses at least.)

According to Brown, the Notturno was not published until 1826. The duet arrangement seems to have appeared around 1816, though, so presumably the full score/parts are meant...